1. Field
One embodiment of the present invention relates to a method of manufacturing a magnetic recording medium, in particular a patterned medium, and the magnetic recording medium manufactured by this method.
2. Description of the Related Art
In the information-oriented society in recent years, the amount of information that needs to be stored in a recording medium has been continually increasing. To keep up with the increase in amount of data, there has been a demand for a recording medium and a recording apparatus with a dramatically high recording density. As regards a hard disk for which there is an increasing demand as a high-capacity and inexpensive magnetic recording medium, it is predicted that a recording density of one terabits per square inch or more, which is about ten times higher than the current recording density, will be required several years after.
In an existing magnetic recording medium used in a hard disk, one bit is recorded in a specific region of a thin film made of polycrystals of fine magnetic grains. To raise the recording capacity of the magnetic recording medium, therefore, the recording density must be increased. For this purpose, a recording mark size usable in recording per bit must be reduced. If, however, the recording mark size is simply reduced, effect of recording noise caused by the shape of fine magnetic grains cannot be neglected. Instead, if the fine magnetic grains are further reduced in size, it is impossible to maintain the information recorded in fine magnetic grains at an ordinary temperature due to thermal fluctuation.
To avoid these problems, it is proposed to use a discrete bit-type patterned medium in which recording dots are separated by a nonmagnetic material in advance so as to perform read and write using a single recording dot as one recording cell.
Also, in the magnetic recording medium incorporated into a hard disk drive (HDD), there is an increasing problem of disturbance of enhancement of track density due to interference between adjacent tracks. In particular, a serious technical subject is reduction of write blurring due to fringe effect of magnetic fields from a write head. To solve such a problem, for example, a discrete track recording-type patterned medium (DTR medium) has been proposed in which recording tracks are physically separated. The DTR medium is capable of reducing a side erase phenomenon of erasing information of an adjacent track in writing or a side read phenomenon of reading out information of an adjacent track in reading, and is capable of enhancing the track density. Therefore, the DTR medium is expected as a magnetic recording medium capable of providing a high recording density. It should be noted that the term “patterned medium” includes a discrete bit type patterned medium and a DTR medium, in a broader sense.
To read and write a DTR medium with a flying head, it is desired to flatten the surface of the DTR medium. Specifically, in order to process a perpendicular magnetic recording layer with a thickness of 20 nm into a patterned medium, grooves with a depth of 20 nm are formed. On the other hand, since the designed flying height of the flying head is about 10 nm, the head may contact the patterned medium when deep grooves are left behind. Accordingly, it has been attempted to fill the recesses between magnetic patterns with a nonmagnetic material so as to flatten the medium surface.
In order to fill recesses between magnetic patterns and flatten the surface, it has been known to deposit, for example, SiO or SiO2 by RF sputtering (Jpn. Pat. Appln. KOKAI Publication No. 2006-236474).
However, since an oxygen-containing gas is used in the conventional method for RF sputtering of the nonmagnetic material, there is a problem the sidewalls of the magnetic patterns may be damaged by oxidation. In addition, process dusts may be produced or thickness dispersion of the nonmagnetic material may be caused by RF sputtering using the oxygen-containing gas.